Crown Prince Abdullah has effectively ruled Saudi Arabia since King Fahd, his elder half-brother, suffered a stroke in 1995.

But despite his prominent position and control of a quarter of the world's oil reserves, remarkably little is known about the crown prince.

His entry in "Who's Who" runs to a meagre seven lines.

Since 1995 he has grown into his role as de facto leader, enjoying widespread credibility among his people and winning praise from Saudi liberals for advocating reform .

Prince Abdullah's exact birth date is unknown, but he is widely believed to have been born in 1923, one of 37 sons - by 16 wives - of the late King Abd al-Aziz.

Since 1995 he has grown into his role as de facto leader and enjoys widespread credibility among his people

He was brought up in the desert according to Bedouin tradition, and learned their rugged and frugal lifestyle.

Today he drives a Rolls Royce with the registration 001, but his public image is one of relative piety in contrast to some of his more flamboyant contemporaries.

Limited reform

At 79 years old, the crown prince remains a physically imposing presence, but is known as a gentle man. A chain smoker, he speaks with a stutter and is far less austere than other Saudi leaders.

Saudi Arabia remains a deeply traditional country

He reportedly greeted journalists arriving for a recent press conference in his garden wearing training shoes.

He has allowed mild criticism of the government in the press, and hinted that more women should be allowed to work.

Saudi traditionalists appreciate his forthright manner, and welcomed his recent criticism of the United States' foreign policy, particularly in the Middle East, Afghanistan and Iraq.

In the run up to the US-led invasion of Iraq, the Saudis said they would not allow American planes to carry out air strikes from the Prince Sultan base in Saudi Arabia without a United Nations resolution authorising war.

The Saudi refusal was reported to have created a rift between Riyadh and Washington.